1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/kernel.h>
3 #include <linux/init.h>
4 #include <linux/clocksource.h>
5 #include <linux/clockchips.h>
6 #include <linux/sched_clock.h>
7 #include <linux/interrupt.h>
8 #include <linux/irq.h>
9 #include <linux/io.h>
10 #include <asm/mach/time.h>
11 #include "soc.h"
12 #include "platform.h"
13
14 /*************************************************************************
15 * Timer handling for EP93xx
16 *************************************************************************
17 * The ep93xx has four internal timers. Timers 1, 2 (both 16 bit) and
18 * 3 (32 bit) count down at 508 kHz, are self-reloading, and can generate
19 * an interrupt on underflow. Timer 4 (40 bit) counts down at 983.04 kHz,
20 * is free-running, and can't generate interrupts.
21 *
22 * The 508 kHz timers are ideal for use for the timer interrupt, as the
23 * most common values of HZ divide 508 kHz nicely. We pick the 32 bit
24 * timer (timer 3) to get as long sleep intervals as possible when using
25 * CONFIG_NO_HZ.
26 *
27 * The higher clock rate of timer 4 makes it a better choice than the
28 * other timers for use as clock source and for sched_clock(), providing
29 * a stable 40 bit time base.
30 *************************************************************************
31 */
32 #define EP93XX_TIMER_REG(x) (EP93XX_TIMER_BASE + (x))
33 #define EP93XX_TIMER1_LOAD EP93XX_TIMER_REG(0x00)
34 #define EP93XX_TIMER1_VALUE EP93XX_TIMER_REG(0x04)
35 #define EP93XX_TIMER1_CONTROL EP93XX_TIMER_REG(0x08)
36 #define EP93XX_TIMER123_CONTROL_ENABLE (1 << 7)
37 #define EP93XX_TIMER123_CONTROL_MODE (1 << 6)
38 #define EP93XX_TIMER123_CONTROL_CLKSEL (1 << 3)
39 #define EP93XX_TIMER1_CLEAR EP93XX_TIMER_REG(0x0c)
40 #define EP93XX_TIMER2_LOAD EP93XX_TIMER_REG(0x20)
41 #define EP93XX_TIMER2_VALUE EP93XX_TIMER_REG(0x24)
42 #define EP93XX_TIMER2_CONTROL EP93XX_TIMER_REG(0x28)
43 #define EP93XX_TIMER2_CLEAR EP93XX_TIMER_REG(0x2c)
44 #define EP93XX_TIMER4_VALUE_LOW EP93XX_TIMER_REG(0x60)
45 #define EP93XX_TIMER4_VALUE_HIGH EP93XX_TIMER_REG(0x64)
46 #define EP93XX_TIMER4_VALUE_HIGH_ENABLE (1 << 8)
47 #define EP93XX_TIMER3_LOAD EP93XX_TIMER_REG(0x80)
48 #define EP93XX_TIMER3_VALUE EP93XX_TIMER_REG(0x84)
49 #define EP93XX_TIMER3_CONTROL EP93XX_TIMER_REG(0x88)
50 #define EP93XX_TIMER3_CLEAR EP93XX_TIMER_REG(0x8c)
51
52 #define EP93XX_TIMER123_RATE 508469
53 #define EP93XX_TIMER4_RATE 983040
54
55 static u64 notrace ep93xx_read_sched_clock(void)
56 {
57 u64 ret;
58
59 ret = readl(EP93XX_TIMER4_VALUE_LOW);
60 ret |= ((u64) (readl(EP93XX_TIMER4_VALUE_HIGH) & 0xff) << 32);
61 return ret;
62 }
63
64 static u64 ep93xx_clocksource_read(struct clocksource *c)
65 {
66 u64 ret;
67
68 ret = readl(EP93XX_TIMER4_VALUE_LOW);
69 ret |= ((u64) (readl(EP93XX_TIMER4_VALUE_HIGH) & 0xff) << 32);
70 return (u64) ret;
71 }
72
73 static int ep93xx_clkevt_set_next_event(unsigned long next,
74 struct clock_event_device *evt)
75 {
76 /* Default mode: periodic, off, 508 kHz */
77 u32 tmode = EP93XX_TIMER123_CONTROL_MODE |
78 EP93XX_TIMER123_CONTROL_CLKSEL;
79
80 /* Clear timer */
81 writel(tmode, EP93XX_TIMER3_CONTROL);
82
83 /* Set next event */
84 writel(next, EP93XX_TIMER3_LOAD);
85 writel(tmode | EP93XX_TIMER123_CONTROL_ENABLE,
86 EP93XX_TIMER3_CONTROL);
87 return 0;
88 }
89
90
91 static int ep93xx_clkevt_shutdown(struct clock_event_device *evt)
92 {
93 /* Disable timer */
94 writel(0, EP93XX_TIMER3_CONTROL);
95
96 return 0;
97 }
98
99 static struct clock_event_device ep93xx_clockevent = {
100 .name = "timer1",
101 .features = CLOCK_EVT_FEAT_ONESHOT,
102 .set_state_shutdown = ep93xx_clkevt_shutdown,
103 .set_state_oneshot = ep93xx_clkevt_shutdown,
104 .tick_resume = ep93xx_clkevt_shutdown,
105 .set_next_event = ep93xx_clkevt_set_next_event,
106 .rating = 300,
107 };
108
109 static irqreturn_t ep93xx_timer_interrupt(int irq, void *dev_id)
110 {
111 struct clock_event_device *evt = dev_id;
112
113 /* Writing any value clears the timer interrupt */
114 writel(1, EP93XX_TIMER3_CLEAR);
115
116 evt->event_handler(evt);
117
118 return IRQ_HANDLED;
119 }
120
121 void __init ep93xx_timer_init(void)
122 {
123 int irq = IRQ_EP93XX_TIMER3;
124 unsigned long flags = IRQF_TIMER | IRQF_IRQPOLL;
125
126 /* Enable and register clocksource and sched_clock on timer 4 */
127 writel(EP93XX_TIMER4_VALUE_HIGH_ENABLE,
128 EP93XX_TIMER4_VALUE_HIGH);
129 clocksource_mmio_init(NULL, "timer4",
130 EP93XX_TIMER4_RATE, 200, 40,
131 ep93xx_clocksource_read);
132 sched_clock_register(ep93xx_read_sched_clock, 40,
133 EP93XX_TIMER4_RATE);
134
135 /* Set up clockevent on timer 3 */
136 if (request_irq(irq, ep93xx_timer_interrupt, flags, "ep93xx timer",
137 &ep93xx_clockevent))
138 pr_err("Failed to request irq %d (ep93xx timer)\n", irq);
139 clockevents_config_and_register(&ep93xx_clockevent,
140 EP93XX_TIMER123_RATE,
141 1,
142 0xffffffffU);
143 }
144
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.